1. Field of the Invention
The present invention relates to a method and apparatus for winding magnetic tape in various situations such as winding a predetermined length of a tape equal in width to the finished product from a bulk roll onto a small tape winding device, rewinding a magnetic tape from one winding device to another, or slitting a web broader than the finished product into widths of the finished product and winding them around a plurality of winding devices.
2. Background Art
Manufacture of magnetic tapes for use as audio cassette tape, video cassette tape, memory tape and broadcasting video tape include intermediate processing steps such as: winding a very long tape from a bulk roll onto small tape winding devices (e.g., reels, hubs and spools) in predetermined lengths; rewinding a magnetic tape from one winding device to another; and slitting a web broader than the finished product into equal widths appropriate for the finished product and winding them around a plurality of winding devices.
In these winding or rewinding steps, if either the physical properties of the tape on a bulk roll on the feed side, or the tape winding device on the takeup side, or the magnetic tape itself are not appropriate, the "behavior" of the tape being wound up will experience variations as manifested by fluctuations in the thickness and width directions of the tape. These changes in tape behavior present serious problems associated with the appearance of the wound tape in that the tape edge as seen in the axial direction of the winding device is irregular and jagged. This phenomenon is particularly pronounced when the tape is running at high speed during winding.
In addition to its poor appearance, such an irregularly wound tape is liable to be damaged at the tape edge. The damage will induce various troubles such as degraded electromagnetic conversion characteristics. The influence of irregular winding is particularly serious with magnetic tapes, such as video tape, which are intended for high-density recording because audio signals and tracking control signals are recorded in the vicinity of the edge of these tapes.
In order to avoid irregular winding, it is normal in the conventional manufacture of magnetic tape to visually check every winding device, for example after the tape has been wound or rewound around it. However, the cost and time required for such inspection is quite substantial and has represented a bottleneck in the production of magnetic tapes.
With a view to reducing this inspection burden and yet achieving a neatly wound tape, those magnetic tapes which potentially have a high rejection ratio in terms of their appearance after winding have been wound by the "finish winding" method operating on the mechanism depicted in FIGS. 7 and 8.
FIGS. 7 and 8 are perspective views showing schematically the components positioned around a takeup winding device (reel) 2 in two types of such a finish winding mechanism. In the mechanism shown in FIG. 7, a flexible endless belt 11 that is typically made of rubber or polyimide and which is rotatably supported on rollers 12, 13 and 14 travels with magnetic tape T as it elastically urges the magnetic surface of T toward the winding device 2 in its radial direction, thereby permitting the tape T to be wound in a neat shape. In the mechanism shown in FIG. 8, a belt 15 made of a comparatively soft nonwoven fabric or a like material is provided between one flange of the winding device 2 and the edge of the tape T facing the flange of the winding device 2. The belt 15 serves to permit the tape T to be neatly wound by urging the edge of one end the winding tape T as the belt 15 is slowly rewound at a constant speed from a delivery side 16 to a takeup side 18 and as it is being guided on rollers 17.
In either type of the mechanism shown, the finish winding belt 11 or 15 makes direct contact with the magnetic tape T and sometimes fails to achieve its intended function in that it causes dropouts as a result of the abrasion of the magnetic layer or the shedding of fibers from the nonwoven fabric Also, it may deform the tape T or damage its edge when subjected to an inappropriate urging pressure In addition, the conventionally employed finish winding mechanism rapidly wears out and poses a problem in terms of both economy and maintenance. Another disadvantage results from the fact that the finish winding mechanism must be so designed that it is displaced to an inactive position before replacement of a different tape winding device 2 and to an active position after the replacement has been completed. This design leads to a complicated winding apparatus and increases the time required for achieving replacement of tape winding devices, which is a definite obstacle to improvement of the production rate of magnetic tapes.
Two methods are currently employed to wind modern cassette tapes. One is the "open" winding method wherein the magnetic tape that has been wound by the above-described finish winding method is installed in a cassette to make a finished product The other method is generally referred to as "in-cassette" winding (or C-0 or V-O winding according to the trade terms) wherein magnetic tape is wound up in the final stage of the cassette assembly line.
An apparatus used to implement the "in-cassette" winding method is shown schematically in FIGS. 9 and 10. All of the necessary components other than the magnetic tape are first assembled into a cassette 23. Subsequently, a tape reel 2 on the delivery end which is pre-connected by a short leader tape 10 to another reel 3 on the takeup end and the reel 3 are inserted into the cassette 23 and screwed down to thereby provide a work piece (which is commonly referred to as V-O or C-O) The leader tape 10 is drawn from both reels 2 and 3 and out the cassette with an "in-cassette" winder and cut into two halves. One half of the leader tape 10 is spliced to one end of the magnetic tape T to be wound up while the other half is retained on a suction member 22. The delivery reel 2 for the spliced tape is rotated until a predetermined length of tape T has been wound up. After the wound tape is cut, the end point of the tape T is spliced to the other half of the leader tape 10 so as to provide a completed product. Because of the absence of any mechanical contact with the magnetic tape in each winding device, the neatness of the tape which has been wound by the "in-cassette" method is totally dependent upon the physical properties of the tape and possible variance in the quality of individual cassette components. This complete failure to achieve control over the neatness of wound tape has been responsible for the very high rejection ratios encountered in the use of the "in-cassette" winding method. With a view to enabling the winding of magnetic tape to produce in a neat final shape, a roller 24 having flanges 25 on both ends is provided at the entrance of the cassette through which the magnetic tape is wound and attempts have been made to urge the tape to one flange on the roller by exerting a force in the direction of the tape width. As it turned out, however, this approach is virtually useless and the "in-cassette" winding method is still in the state of lacking any effective means for permitting the magnetic tape to be wound in a satisfactorily neat overall shape.